The present invention relates to a device for feeding and checking layers of cigarettes in cigarette packaging machines. More precisely, the device comprises a combination of means which check the completeness and soundness of the layers of cigarettes which are superimposed to form the complete bundles subsequently fed to the wrapping means of the packaging machine. In particular, an apparatus in accordance with Italian Pat. No. 803,345 of the same applicant is known, comprising a feed hopper for the cigarettes.
Said hopper is devided at its bottom into a number of branches or elementary hoppers equal to the number of layers of cigarettes constituting a complete bundle to be packaged.
Each elementary hopper is provided internally with baffles forming channels of width slightly greater than the diameter of a cigarette, and of a number equal to the number of cigarettes which constitute the corresponding layer.
At the bottom or discharge mouth of each of said elementary hoppers there is provided a station for receiving said layers of adjacent cigarettes, which are then fed individually by a pusher device into compartments in an endless conveyor which is driven intermittently. Said bundles are gradually formed in said compartments by superimposing the layers one on the other.
At the end of this operation, it is not infrequent to find incomplete bundles inside the compartments in said endless conveyor.
According to the known art, in order to detect such defective bundles, which are then ejected, electromechanical devices are used comprising sensing members consisting of feeler pins opposed by resilient means.
These pins press axially against the ends of the cigarettes, to check not only their presence but also their correct degree of end filling, and the correctness of their longitudinal dimensions. These devices can carry out their checking action, as described in Italian Pat. No. 921,005 of the same applicant, either in said channels or alternatively in the path of the said endless conveyor.
The result of this checking operation is then transmitted via a memory device both to a device for ejecting the defective groups disposed in the path of said endless conveyor, and to the feed means for the various wrapping materials and sealing labels, so that they suspend delivery relative to the ejected bundles. However, it frequently happens that incomplete bundles are not detected by said electromechanical devices.
This is due to the fact that in the case, for example, of the absence of a cigarette, two adjacent feeler pins can become pressed simultaneously by one and the same cigarette which has become disposed in an irregular position because of the absence of an adjacent cigarette.
Optical devices are also known for checking the completeness of the bundles.
In these latter devices, which are normally located in the path of said endless conveyor, one end of each cigarette making up the bundle is illuminated by a light beam directed along its axis. Photosensitive elements are provided facing the other ends of the cigarettes, and if one or more cigarettes are absent, these become illuminated and activate a device for ejecting the defective group.
A considerable disadvantage of these latter devices derives however from the fact that during the described operations, a certain quantity of tobacco dust is released from the cigarettes. This dust inevitably deposite on said photosensitive elements or on any transparent protection elements, making them insensitive to light and reducing the effectiveness of the entire checking device.
In addition, these optical checking devices are not able to check the exactness of the longitudinal dimensions of the individual cigarettes, in that even shorter cigarettes (for example lacking the filter) intercept the light beams directed towards the photosensitive elements to the same extent as the other cigarettes of the bundle.